Colloids versus crystalloids in the prevention of hypotension induced by spinal anesthesia in elective cesarean section. A systematic review and meta-analysis.

The incidence of hypotension associated to spinal anesthesia in elective cesarean section is high. To determine the effects of colloids and crystalloids in the incidence of hypotension induced by spinal anesthesia in elective cesarean section, an attempt was made to define which type of fluid and what total volume should be administered. Following the PRISMA methodology a systematic review and meta-analysis were carried out. A systematic Medline/PubMed, EMBASE and Cochrane Library search was made to identify trials where women were scheduled for elective cesarean section with spinal anesthesia and volume loading (preload or co-load). The primary outcome was the incidence of hypotension. Stratification into subgroups was made for the primary outcome according to the type of colloid administered, differentiating those studies employing new generation colloids (HES 6% 130/0.4) from those not using such colloids, based on the volume of colloid administered and the combination of a vasopressor. The secondary outcome was the incidence of intraoperative nausea and vomiting. Two-hundred and twenty-seven controlled clinical trials were analyzed; eleven randomized clinical trials including 990 patients were included. A significative decrease of incidence of hypotension associated to spinal anesthesia was observed with the use of colloids compared to crystalloids (RR [95% CI] 0.70 [0.53-0.92], P=0.01). However, there was no difference between crystalloid and colloid in the risk of intraoperative nausea and vomiting (RR [95% CI] 0.75 [0.41-1.38]; P=0.33). This meta-analysis shows colloid administration to significantly reduce the incidence of hypotension associated to spinal anesthesia in elective cesarean section compared with of crystalloid use.